It is my understanding at the end of the mash I must 'mash out', i.e. cause the enzymes to stop working. From what I have read liquor(water) heated to 170 degrees F will accomplish this task.
Can I heat my sparge water to 170 degrees and 'mash out' and sparge at the same time? Does the sparge water need to be maintained at 170 degrees throughout the sparge, or can it cool? That is to say, do I need to have an additional insulated container to hold the sparge water, or will an old bottling bucket suffice?
Nate

mashing out is an important step, but from what I have concluded it is notimportant because of enzyme deactivation.

If you think about it, your sweetliquor will be extracted and the brought to a boil for 60 minutes or more. Really, is there any point worrying about deactivating the enzymes a little sooner. if you are ending up with a wort that is too fermentable, mash at a slightly higher temperature to favor dextrine formation.

The real reason the mashout is important (and 168-170 F is the right target temperature for bringing your mash to at this point

When you mash out, you raise the temperature of the mash to 168F (170F) which is the temperature that is most desired for maximum extraction. Lower temperatures result in less efficiency, higher temperatures begin to extract harsh flavors. Thus you raise the temperature to 168F first and then try to maintain that temperature through the lautering process.
The sparge water has to be hot enough to maintain your optimum extraction temperature but this can be difficult for a home brewer to accurately control. Even if the water is the right temp when it leaves the vessel, by the time it trickles through the hose and sprinkles over the grain bed, the temperature may have dropped significantly.
You will have to see what works best with your own system. You may start out with hotter sparge water to compensate for heat loss. Or you can just do your reasonable best and not worry too much about less than optimum temperatures. If anything, stay away from temperatures that are too high; a little lower is better than a little higher in my opinion.
I usually heat my own sparge water to about 175F and this seems to work for me. My sparge vessel is a stainless pot that has its own burner. Before I used that, I used a plastic bucket; a little less convenient but it worked.

In a larger setting (4 barrels or greater) run-off takes longer (English brewers tend to run-off at a much slower rate than we do in the U.S.), so the enzymes would continue to work which would change the charateristics of the wort and your finished beer. So if you are running off 'small' volumes of wort and starting your sparge at 170 deg F. your mash should set fine. You can let your sparge water cool as you run off but adjust the pH to 5.2-5.6.